Field
The present disclosure relates to a lithium ion secondary battery diagnosis device and a lithium ion secondary battery diagnosis method, more particularly, a technique of diagnosing whether or not there is abnormality in a battery pack including lithium ion secondary batteries by measuring AC impedance.
Description of the Background Art
A battery pack is mounted on an electrically powered vehicle such as a hybrid vehicle. When a period of use of the battery pack exceeds a predetermined period (or when a total traveling distance of the electrically powered vehicle exceeds a predetermined distance), it is desirable to diagnose whether or not there is abnormality in the battery pack as a part of maintenance for the electrically powered vehicle. Moreover, when discharging the electrically powered vehicle, it is desirable to diagnose whether or not there is abnormality in the battery pack in order to find whether or not the battery pack is reusable. For example, Japanese Patent Laying-Open No. 2009-277627 discloses a technique of diagnosing whether or not each of cells included in the battery pack is abnormal based on the discharging voltage of the cell detected when completely discharging the cell.